1. Field of the Invention
Aspects of the present invention relate, in general, to an image forming apparatus and, more particularly, to an image forming apparatus, in which a developer can be efficiently saved.
2. Description of the Related Art
In general, an image forming apparatus includes a paper feeder, an image forming unit, a fixer and a paper discharger. The paper feeder supplies a print paper to the image forming unit, which then selectively coats a developer on the print paper to form a desired image. The fixer fixes the coated developer on the print paper. The paper discharger receives the print paper with the developer fixed from the fixer and discharges it to the outside.
The image forming unit includes a photosensitive drum, a developing roller and a transfer roller to form an image through a desired developing process. A light scanning unit scans a light containing information of a printing image on the photosensitive drum to form an electrostatic latent image thereon. A desired developing bias is applied between the developing roller and the photosensitive drum to thereby form a potential difference in-between. The developing roller selectively supplies the developer on the electrostatic latent image of the photosensitive drum and the transfer roller transfers the developer coated on the photosensitive drum to the print paper.
In general, the developer is stored in a developer storage, which is detachably attached to the main assembly of the image forming apparatus. The developer is stored in the developer storage and supplied to the developing roller. If the entire developer stored in the developer storage is used, a user can remove the developer storage and replace it with a new one filled with developer, or re-fill the developer storage with new developer.
In order to reduce the replacement cost or re-filling cost of a developer storage, an image forming apparatus is provided with a printing mode capable of saving the developer. In the case of this saving mode, more printing jobs can be performed, as compared with a normal mode, although the quality of printing image is degraded. Furthermore, the printing images may not always require a good image quality, i.e., may require a different quality of images, depending upon a degree of importance for the image to be printed. In the case of a lower degree of importance, the printing job for the image can be performed in a saving mode, thus avoiding waste of the developer.
In the conventional image forming apparatus, the light scanning unit adjusts the intensity of scanning light to thereby weaken the electric potential of an electrostatic latent image formed in the photosensitive drum, so that the quantity of the developer to be coated on the photosensitive drum can be reduced. Alternatively, the developing bias of the developing roller is adjusted to reduce the quantity of the developer to be coated on the photosensitive drum. However, this conventional developing-agent saving method results in complexity of the image forming apparatus and also does not result in a significant impact on the amount of developer which is saved.